1. Field of the Invention
The present invention relates to the testing and monitoring of electronic circuits. More specifically, the present invention relates to test probes used to make measurements in electronic circuits.
2. Description of the Related Art
For the measurement of electronic parameters such as voltage, current, and resistance, many types of test probes have been developed. FIGS. 1a–g (Prior Art) are partial side views of various probe configurations in common use. FIG. 1c (Prior Art) illustrates one of the most common probe configurations, the simple needle type probe 106. While good for making contact with relatively flat surfaces, making measurements on small diameter pins, leads or wires 100 require a tangential contact with the pin's surface. The test probe is then subject to slippage while trying to make the measurement, potentially causing a short circuit with other pins or metal surfaces in the vicinity of the pin 100 being measured; loss of contact with desired test point is also possible. Probes more suitable for making measurements on pins are shown in FIGS. 1a and 1b (Prior Art). FIG. 1b illustrates a simple forked tip 104 which straddles the pin 100 being measured. This solution reduces the potential for disengagement while measuring the pin compared to the method of FIG. 1c, as long as the pin is less that the width of the probe tip. Larger pins cannot be easily accommodated, requiring multiple tips of varying sizes. Additionally, there remains the possibility of slipping along the surface of the pin 100, potentially contacting other nearby circuit components. The probe 102 shown in FIG. 1a is similar to that of FIG. 1b, but generally handles smaller pin diameters. The probes of FIGS. 1a–c have an additional disadvantage in that they require the use of at least one hand of an operator at all times while making a measurement. This “hands on” requirement limits the movement of an operator for making instrument adjustments during a measurement, or causes the operator to repeatedly break contact with the circuit being measured to adjust the meter or oscilloscope. This may lead to reduced productivity or errors when the operator has to repeatedly find a test point in closely spaced circuitry. A common configuration 108 that removes the “hands on” requirement is shown in FIGS. 1d and 1e (Prior Art). This type of probe employs a spring loaded hook 110 that must be opened (FIG. 1d) to capture pin 100. However, this type of probe is difficult to use when the measurement must be made on closely spaced pins or integrated circuit leads, since the spring loaded hook is often significantly larger than the pin diameter. This configuration is also not suitable for making measurements on flat printed circuit board traces. The springs and sliding parts are a source of reliability problems and complexity. Another common configuration of a gripping type of measurement probe 112 is shown in FIGS. 1f and 1g. In this probe spring loaded arms 116a and 116b extend from handle 114 to encircle pin 100. Upon retraction of arms 116a and 116b, pin 100 is captured and held against handle 114. This probe has similar disadvantages to the probe of FIGS. 1d and 1e. In particular, it is easy to short adjacent pins when the probe is in the open position of FIG. 1f, making it difficult to use on closely spaced pins. It is also not suitable for measuring circuit board traces.
FIGS. 2a–2c (Prior Art) are partial side views of current art test probes probing printed circuit boards with closely spaced traces. Of the three configurations 102, 104, and 106, the simple needle probe 106 is best suited to measure circuit board trace 212 on circuit board 200. Forked tip probe 104 can easily short traces 208 and 210, unless the probe tip is made considerably smaller in diameter, which reduces its practicality for measuring a wide variety of pins. The same is true for probe tip 102, which can potentially short traces 202,204, and 206 in FIG. 2a. So, while the simple needle probe 106 is good for circuit board traces, it is difficult to use on pins leads and wires. The forked tip configurations 102 and 104 are acceptable for pins, leads and wires with diameters less than the probe tip dimension, but they are not easily applied to measure closely spaced circuit board traces.
What is needed is a simple, flexible probe that can measure both pins and circuit board traces without causing shorts, grips pins tightly without slipping, provides “hands off” measurement capability, and has no wearable moving parts.